1. Field of the Invention
The present invention relates to light-emitting devices. More particularly, the invention relates to a light-emitting device which includes an organic electroluminescent element (hereinafter appropriately referred to as the “organic EL element”).
2. Description of the Related Art
The light-emitting device with an organic EL element can have a planar shape and provide light of white color or a color close thereto. Accordingly, the light-emitting device with an organic EL element is thought to be employed for use as, e.g., a light source of a lighting apparatus for lighting space in living environments, or a backlight unit for display devices.
However, the currently known organic EL element is too low in efficiency to be employed for the aforementioned lighting use. In this context, it is desired to improve the light extraction efficiency of the organic EL element. Known as a method for providing the organic EL element with an improved light extraction efficiency is to provide a surface of the organic EL element of a single-side emission type with various types of concavo-convex structures. For example, it is proposed to provide a surface of the organic EL element with a structure layer having a concavo-convex structure (see Patent Literature 1). This concavo-convex structure can achieve the favorable collection of light, providing enhancement in the aforementioned light extraction efficiency.